Drug delivery pump drive using a shaped memory alloy wire

ABSTRACT

A pump drive and a method thereof to dispense a liquid drug from a container having a plunger piston are disclosed. The pump drive provides a unidirectional clutch provided about a rotational axis which supports centrally a wheel. The clutch has an inner race operably connected to the plunger piston, wherein the clutch is configured to rotate both the inner race about the axis in unison with rotation of the wheel in only a first direction to advance the plunger piston, and to let the wheel rotate relative to the inner race about the axis in a second direction opposite to the first direction without advancing the piston plunger. The drive in one embodiment includes at least one shape memory alloy wire which when excited rotates the wheel in the first rotational direction to advance the piston plunger and dispense the liquid drug from the container.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of currently pending U.S. applicationSer. No. 13/460,087 filed Apr. 30, 2012 which is a divisional of U.S.application Ser. No. 12/120,672 filed May 15, 2008.

FIELD OF THE INVENTION

The present invention is generally related to drug delivery pumps, andin particular to a drug delivery pump drive using a shape memory alloyto advance a plunger piston to deliver a liquid drug from a container.

BACKGROUND OF THE INVENTION

Typically miniature drug delivery pumps use an electric motor and asystem of many gears to reduce the high speed motors down to a slowerspeed. The slower speed provides the precision needed to control thevery small doses of a liquid drug being delivered by means of anadvancing lead screw and nut moving the syringe piston. Due to the aboveperformance requirements, such miniature drug delivery pumps use anexpensive high quality electric motor and the associated high qualitygears, therefore making such pumps expensive and generally notdisposable in nature. In addition, concealment under clothing isproblematic due to the relative size of the motor and the noisegenerated during operation.

SUMMARY OF THE INVENTION

It is against the above background that the present invention provides adrug delivery pump drive which uses a shape memory alloy (SMA) toadvance a plunger piston to deliver a liquid drug from a container and amethod thereof. The small size of the SMA based pump drive helps toreduce overall size of the drug delivery pump, thereby resulting in asuitable wearable device. In addition, due to the low cost of the SMAbased pump drive, the drug delivery pump may be disposable.

The present invention in one embodiment provides a SMA based pump drivefor a miniature drug delivery pump having a single SMA wire used todrive a main wheel in a driven direction and a spring to rewind the mainwheel after each drive cycle. In another embodiment, the SMA based pumpdrive provides a pair of SMA wires which are wrapped around thecircumference of the main wheel in opposite directions and connectedthereto so that one SMA wire rotates the main wheel clockwise and theother SMA wire rotates the wheel counter clockwise when excitedsequentially. In another embodiment, the SMA based pump drive provides aplurality of the above mentioned opposed pairs of the SMA wires. Instill another embodiment of the SMA based pump drive, a SMA wire isprovided in a linear solenoid arrangement with a spring return toprovide reciprocating linear motion. A set of concentric (inner andouter) tubes having matching facing helical slots with bearingstherebetween is provided to convert the reciprocating linear motion intoreciprocating rotary motion. As the SMA wire and spring return linearlyreciprocate, pulling the inner tube therewith, the helical slots andbearings between the inner and outer tubes cause the outer tube torotate a few degrees back and forth for each drive cycle. The outer tubebeing connected to the main wheel, transfers this clockwise andcounterclockwise (reciprocating rotary) motion for each drive cycle tothe main wheel. Inside the main wheel is a unidirectional clutch whichconverts the reciprocating rotary motion of the main wheel intorotational motion in a single direction. This rotational motion in asingle direction is used to advance a lead screw and push the plungerpiston to dispense the liquid drug from the container.

In another embodiment, a pump drive used to dispense a liquid drug froma container having a plunger piston is disclosed. The pump drivecomprises a unidirectional clutch provided about a rotational axis andsupporting centrally a wheel. The unidirectional clutch has an innerrace operably connected to the plunger piston, wherein theunidirectional clutch is configured to rotate both the inner race aboutthe rotational axis in unison with rotation of the wheel in only a firstrotational direction which advances the plunger piston, and to let thewheel rotate relative to the inner race about the rotational axis in asecond rotational direction opposite to the first rotational directionwithout advancing the plunger piston. The pump drive also includes atleast one shape memory alloy wire providing a motor force when excitedto rotate the wheel in at least the first rotational direction.

In still another embodiment, a pump drive used to dispense a liquid drugfrom a container having a plunger piston is disclosed. The pump drivecomprises a lead screw having a rotational axis and being operablyconnected to the plunger piston wherein rotation of the lead screw aboutthe rotational axis advances the piston plunger in a dispensingdirection which dispenses the liquid drug from the container, a wheel,and a unidirectional clutch provided about the rotational axis andsupporting centrally the wheel. The unidirectional clutch has an innerrace connected centrally to the lead screw, wherein the unidirectionalclutch is configured to rotate both the inner race and lead screw aboutthe rotational axis in unison with rotation of the wheel in only a firstrotational direction, and to let the wheel rotate relative to the innerrace without rotating the lead screw about the rotational axis in asecond rotational direction opposite to the first rotational direction.The pump drive further includes at least one shape memory alloy wireproviding a motor force when excited to rotate the wheel in at least thefirst rotational direction.

In another embodiment, a pump drive used to dispense a liquid drug froma container having a plunger piston is disclosed. The pump drivecomprises a unidirectional clutch provided about a rotational axis andsupporting centrally a wheel. The unidirectional clutch has an innerrace operably connected to the plunger piston, wherein theunidirectional clutch is configured to rotate both the inner race aboutthe rotational axis in unison with rotation of the wheel in only a firstrotational direction which advances the plunger piston, and to let thewheel rotate relative to the inner race about the rotational axis in asecond rotational direction opposite to the first rotational directionwithout advancing the plunger piston. The pump drive also includes alinear drive to rotate the wheel in the second rotational direction, anda pair of inner and outer concentric tubes with helical slots andbearings therebetween located about the axis of rotation. In thisembodiment, the linear drive acts on the inner tube in opposition suchthat the inner tube reciprocates with linear motion along the axis ofrotation, wherein the helical slots and bearings cause the outer tube toreciprocate with rotary motion about the axis of rotation as the innertube reciprocates with linear motion along the axis of rotation, andwherein the outer tube is connected to the wheel such that the rotarymotion of the outer tube causes the wheel to rotate in the firstrotational direction and then in the second rotational direction.

In another embodiment, a method of dispensing a liquid drug from acontainer having a plunger piston is disclosed. The method comprisesproviding a unidirectional clutch about a rotational axis which supportscentrally a wheel, the unidirectional clutch having an inner raceoperably connected to the plunger piston, wherein the unidirectionalclutch both rotates the inner race about the rotational axis in unisonwith rotation of the wheel in only a first rotational direction whichadvances the plunger piston, and lets the wheel rotate relative to theinner race about the rotational axis in a second rotational directionopposite to the first rotational direction without advancing the plungerpiston. The method also includes providing a motor force by exciting atleast one shape memory alloy wire which rotates the wheel in at leastthe first rotational direction.

In still another embodiment, a method of dispensing a liquid drug from acontainer having a plunger piston is disclosed. The method comprisesproviding a unidirectional clutch about a rotational axis which supportscentrally a wheel, the unidirectional clutch having an inner raceoperably connected to the plunger piston, wherein the unidirectionalclutch both rotates the inner race about the rotational axis in unisonwith rotation of the wheel in only a first rotational direction whichadvances the plunger piston, and lets the wheel rotate relative to theinner race about the rotational axis in a second rotational directionopposite to the first rotational direction without advancing the plungerpiston; providing a linear drive to rotate the wheel in the secondrotational direction. The method also includes providing a pair of innerand outer concentric tubes with helical slots and bearings therebetweenlocated about the axis of rotation, wherein the linear drive acts on theinner tube in opposition such that the inner tube reciprocates withlinear motion along the axis of rotation, wherein the helical slots andbearings cause the outer tube to reciprocate with rotary motion aboutthe axis of rotation as the inner tube reciprocates with linear motionalong the axis of rotation, and wherein the outer tube is connected tothe wheel such that the rotary motion of the outer tube causes the wheelto rotate in the first rotational direction and then in the secondrotational direction.

In yet another embodiment, a method of dispensing a liquid drug from acontainer having a plunger piston is disclosed. The method comprisesproviding a lead screw having a rotational axis and operably connectingthe lead screw to the plunger piston wherein rotation of the lead screwabout the rotational axis advances the piston plunger in a dispensingdirection which dispenses the liquid drug from the container, providinga wheel, and providing a unidirectional clutch to support the wheelabout the rotational axis. The method further includes connecting aninner race of the unidirectional clutch centrally to the lead screw,wherein the unidirectional clutch is configured to rotate both the innerrace and lead screw about the rotational axis in unison with rotation ofthe wheel only in a first rotational direction, and to let the wheelrotation relative to the inner race without rotating the lead screwabout the rotational axis in a second rotational direction opposite tothe first rotational direction; providing at least one shape memoryalloy wire which when excited provides a motor force to rotate the wheelin at least the first rotational direction; and exciting the shapememory alloy wire.

These and other features and advantages of the invention will be morefully understood from the following description of various embodimentsof the invention taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the various embodiments of thepresent invention can be best understood when read in conjunction withthe following drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 is an end view of one embodiment of a SMA based pump driveaccording to the present invention having a single SMA wire with aspring return and a unidirectional clutch;

FIG. 1A is a schematic view of one embodiment of a SMA based pump driveaccording to the present invention having a plurality of SMA wires witha spring return and a unidirectional clutch.

FIG. 2 is an end view of another embodiment of a SMA based pump driveaccording to the present invention having an opposed pair of SMA wiresand a unidirectional clutch;

FIG. 2A is a section view of the embodiment shown by FIG. 2 and takenalong section line 2A-2A;

FIG. 3 is an end view of still another embodiment of a SMA based pumpdrive according to the present invention having a plurality of opposedpairs of SMA wires and a unidirectional clutch;

FIG. 4 is an exploded view of yet another embodiment of a SMA based pumpdrive according to the present invention having a coiled SMA wire with aspring return driving a pair of concentric tubes and a unidirectionalclutch;

FIG. 5 is an exploded view of an embodiment of a miniature drug deliverypump according to the present invention and shown with the SMA basedpump drive shown by FIG. 4;

FIG. 6 is an exploded view of particular components of a SMA based pumpdrive and their arrangement thereof according to the present invention;and

FIG. 7 is a perspective view of the miniature drug delivery pumpembodiment shown by FIG. 5 according to the present invention with anadministration set.

DETAILED DESCRIPTION

It is against the above background that the present invention provides aminiature drug delivery pump which uses a shape memory alloy (SMA) basedpump drive to advance a syringe plunger to deliver a liquid drug from acontainer. The present invention has a cost and size advantage comparedto traditional miniature drug delivery pumps and is a very compact andpotentially disposable pump device design due to cost.

In the following description of the embodiments of the invention,skilled artisans appreciate that elements in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.For example, the dimensions of some of the elements in the figures maybe exaggerated relative to other elements to help to improveunderstanding of embodiment(s) of the present invention. Accordingly,the drawings are merely schematic representations, intending to depictonly typical embodiments of the invention, and therefore should not beconsidered as limiting the scope of the invention. The invention will bedescribed with additional specificity and detail through theaccompanying drawings. The description of the invention may contain, forexample, such descriptive terms as up, down, top, bottom, forward, back,clockwise, counterclockwise, right, or left. These terms are meant toprovide a general orientation of the parts of the invention and are notmeant to be limiting as to the scope of the invention.

Referring now to FIGS. 1-4, various illustrative embodiments of the SMAbased pump drive according to the present invention are shown, andgenerally indicated by symbols 10, 20, 30, and 40, respectively. All ofthese embodiments of the SMA based pump drive 10, 20, 30, and 40 arereciprocating in design which converts linear motion of at least one SMAwire into unidirectional rotary motion.

Shape memory alloys are metals which exhibit two very unique properties,pseudo-elasticity, and a shape memory effect due to the metals havingMartensite (unheated, deformable state) and Austenite (heated, originalshape recovering state) phase changes. In most shape memory alloys, atemperature change of only about 10° C. is necessary to initiate thephase change (Martensite to Austenite) to recover an original size andshape of the wire after elongation and deformation. Alloys used as ashape memory alloy (SMA) wire include, for example and not limitedthereto, copper based alloys, such as for example,copper-zinc-aluminum-nickel, copper-aluminum-nickel,iron-manganese-silicon alloys, and nickel-titanium (NiTi) alloys. Thepresent invention in all embodiments uses at least one SMA wire as aprime mover for a unidirectional clutch which turns in one direction alead screw which translates a plunger piston to dispense a liquid, suchas a drug, from a container or cartridge.

In the first illustrated embodiment of the SMA based pump drive 10 shownby FIG. 1, a shape memory alloy (SMA) wire 12 is fixed at one end 16 toa support 18. The other end 22 of the SMA wire 12 is wrapped around thecircumference and connected to a main wheel 24 (i.e., an outer race) ofa unidirectional clutch 28. Excitation (heating) of the SMA wire 12causes the SMA wire 12 to work to regain its original size and shape,i.e., shorten in length, which rotates the main wheel 24 in a firstdirection about an axis of rotation, indicated by symbol “X”. Afterexcitation and cooling below the Martensite phase temperature, a spring26 re-deforms by bending and elongating the SMA wire 12, and rotates themain wheel 24 in a second opposed direction about the axis of rotation Xto complete a drive cycle. As shown, the spring 26 is also attached tothe support 18 at one end and to the main wheel 24 at the other end atpoint which places the spring 26 in opposition to the contraction of theSMA wire 12 when in the Austenite phase.

In the SMA based pump drive 10 shown by FIG. 1, as with the otherembodiments of the SMA based pump drive 20, 30, and 40 (FIGS. 2, 3, and4, respectively), the excitation of the SMA wire 12 is effected by theapplication of electrical energy from a battery 62 via conductors 14which creates heat through the resistance of the SMA wire 12 itself. Theapplication of the electrical energy from the battery 62 is controlledby a controller 25 which is configured to switch the electrical energyon and off. In one embodiment, the switching is a timed pulse whencommanded by a user to operate, such as for example, via a push button72. In one embodiment, pushing the push button 72 results in thecontroller 25 switching the electrical energy from the battery 62 on andoff such that the SMA wire 12 will complete the correct number of drivecycles to release a defined quantity of the liquid drug. For example, inone embodiment, a push of the push button 72 causes the release of adose of 0.5 ml of insulin. In other embodiments, other dosages per pushof the push button 72 are also possible, which may range from 0.1 ml to1 ml, and will depend on the programming/circuitry of controller 25,degrees of rotation of the main wheel 24 effected by the SMA wire 12,the transmitted torque of the unidirectional clutch 28 to a lead screw32, and threading 41 between the lead screw 32 and a nut portion 43 of aplunger piston 44 (FIG. 6), which advances a plunger piston 44 todispense the liquid drug from a drug container 46 (FIG. 5)

It is to be appreciated that in the SMA based pump drives 10, 20, and 30(FIGS. 1-3, respectively), each SMA wire 12 is orientated adjacent theaxis of rotation X of the main wheel 24, and in one particularembodiment, substantially perpendicular to the axis of rotation X. Inaddition, in the embodiments shown by FIGS. 1-3, each SMA wire 12 iswrapped around at least half of the circumference of the main wheel 24with the end 22 of the SMA wire 12 coupled directly thereto. Forexample, in the illustrated embodiments shown in FIGS. 2 and 3, each SMAwire 12 extends about three quarters of the way around the circumferenceof the main wheel 24 and is coupled to a spoke 31 as best shown by FIG.2A, which is a side portion view of the main wheel 24 taken alongsection line 2A-2A in FIG. 2. In one embodiment, the spoke 31 issituated above a surface portion 33 of the main wheel 24 that isrecessed below the outermost circumference of the main wheel 24 andextends in a direction parallel to the axis of rotation X. In oneembodiment the outermost circumference of the main wheel 24 is definedby front and rear face plate portions 35 a and 35 b, respectively. Asshown in FIG. 2A, the spoke 31 spans between and is mounted atrespective ends to the front and rear face plate portions 35 a and 35 b.The SMA wire 12 connects to the spoke 31 in a conventional fashion, suchas for example, and not limited thereto, welding, screwing, wrapping,clamping, etc.

As shown by FIG. 2, for this embodiment of the SMA based pump drive 20,an opposed pair of SMA wires 12 a and 12 b are connected at their firstends to a respective support 18. At their other ends, the SMA wires 12 aand 12 b are connected to the main wheel 24 in opposition, such that theexcitation of one wire will deform the other and vice-versa, therebycausing cycling of the main wheel 24 in a clockwise and counterclockwise fashion. As the SMA wires 12 a and 12 b are electricallyenergized and controlled as described above with reference to theconductors 14, the controller 25, and the battery 62 shown by FIG. 1,for brevity and ease of illustration, no further discussion or showingthereof in FIG. 2 is provided.

With reference now to FIG. 3, for this SMA based pump drive 30, aplurality of opposed pairs of SMA wires 12 a and 12 b are connectedaround a frame 19 and the circumference of the main wheel 24. In thisillustrated embodiment, each of the SMA wires 12 a and 12 b is alsowrapped at least half way around the main wheel 24 and connectedthereto, such as via spokes 31 as shown in the embodiment depicted inFIG. 2A. The other end of each SMA wire 12 a and 12 b is connected toand about the frame 19 such that opposed pairs of the SMA wires 12 a and12 b act in opposition to each other in the same manner as shown in FIG.2, e.g., providing clockwise rotation and then providingcounterclockwise rotation, or vice versa. In an alternative embodiment,a counteracting spring 26, such as shown by FIG. 1, is provided eithersingularly or a plurality replacing one side of the SMA wires 12 a or 12b about the frame 19 and main wheel 24, such that the SMA wires providerotation in a first direction (e.g., clockwise) and the spring(s) 26provides rotation in a second direction (e.g., counterclockwise). It isto be appreciated that in comparison to the SMA based pump drives 10 and20 (FIGS. 1 and 2, respectively), if similar sized SMA wires are used,the SMA based pump drive 30 of FIG. 3 would provide a larger torque dueto the greater number of similarly sized SMA wires 12. Accordingly,thinner, lower cost SMA wire 12 may be used in the SMA based pump drive30 than the single or double SMA wire embodiments shown by FIGS. 1 and2, and still produce a desired torque. In addition, the SMA based pumpdrive 30 provides a more robust system than the single and double SMAwire embodiments shown by FIGS. 1 and 2, due to the fact that should anyof the SMA wires 12 a or 12 b encounter mechanical failure, the otherremaining opposed pairs of SMA wires 12 a and 12 b will continue toprovide sufficient torque to rotate the main wheel 24 under the providedload and generate the motor force needed to push a plunger piston of aliquid drug container. Accordingly, the SMA based pump drive 30 may beuseful in health situations in which redundancy and reliability ofdelivering a liquid drug is needed. As the opposed pairs of plurality ofSMA wires 12 a and 12 b are electrically energized and controlled asdescribed above with reference to FIG. 2, and via a plurality of therespective conductors 14 tied in parallel to the controller 25 and thebattery 62 shown by FIG. 1, for brevity and ease of illustration, nofurther discussion or showing thereof in FIG. 3 is provided.

For the SMA based pump drive 40 illustrated by FIG. 4, the SMA wire 12is provided as a coil in a linear drive 109 and orientated along theaxis of rotation X of the main wheel 24. The SMA wire 12 is operablycoupled to the main wheel 24 via a linear solenoid arrangement,indicated generally by symbol 110, which includes the linear drive 109.In an alternative embodiment, the linear drive 109 shown in the FIG. 4may be replaced with an electro-magnetic solenoid with a spring return,if faster fluid delivery is a desire.

In the illustrated embodiment, the linear drive 109 includes an actuatorbody 112, which is shown with a portion of a side wall 114 removed toshow the interior components thereof. Housed within the actuator body112 is the coiled SMA wire 12 and a plunge rod 116. The plunge rod 116is housed slidably within the actuator body 112 and fixed for linear(back and forth) motion by a rail portion 118 provided on the side wall114 engaged with a slot 120 provided on the plunge rod 116.Alternatively, the rail portion 118 may be provided on the plunge rod116 and the slot 120 provided on the side wall 114, wherein thisalternative arrangement is illustrated by the shown hidden lines withinthe actuator body 112.

The linear drive 109 of the solenoid arrangement 110 also include aspring return 122 to provide the reciprocating linear motion afterexcitation of the coiled SMA wire 12 as explained above in a previoussection. In the illustrated embodiment, the spring return 122 is aspring housed also within the actuator body 112 in opposition to (i.e.,biased against) the Austenite phase of the coiled SMA wire 12. A set ofconcentric inner and outer tubes 124 and 126, respectively, is alsoprovided by the linear solenoid arrangement 110. An extension portion128 of the plunge rod 116, which extends outwardly and centrally fromthe actuator body 112 connects centrally along the axis of rotation X tothe inner tube 124. In this manner, the reciprocating linear motion ofthe plunge rod 116, due to movement from excitation of the coiled SMAwire 12 and the opposite motion thereafter from the spring return 122,is transferred to the inner tube 124.

The set of concentric inner and outer tubes 124 and 126 are providedwith matching facing helical slots 130 having bearings 132 therebetween,which convert the reciprocating linear motion of the inner tube 124 intoreciprocating rotary motion of the outer tube 126. As the plunge rod 116linearly reciprocates, pulling the inner tube 124 therewith, thebearings 132 between the inner and outer tubes roll in their respectivehelical slots 130 causing the outer tube 126 to rotate a few degreesback and forth for each drive (push-pull) cycle of the plunge rod 116.The outer tube 126 being connected to the main wheel 24, transfers thisclockwise and counterclockwise (rotational) motion for each drive cycleto the main wheel 24.

In one embodiment, the unidirectional clutch 28 is a one-way rollerclutch or Sprag clutch; however, the invention is not limited in thisrespect and may find application with other unidirectional clutches. Insuch an embodiment, as the back and forth oscillation of the main wheel24 occurs, the unidirectional clutch 28 alternately slips in onedirection and then grabs in the opposite direction for each drive cycleof the SMA wire 12. As the unidirectional clutch 28 turns in thenon-slip direction, the lead screw 32, which is connected centrallyalong the axis of rotation X to the clutch 28, also turns in thenon-slip direction.

For example and with reference to FIG. 1, as the main wheel 24 rotatesin the clockwise direction, clutch rollers 34 jam between the main wheel24 and the inner race 36, locking them together. This locking actionallows the angular displacement of the main wheel 24 to be transmittedto the lead screw 32. As the main wheel 24 rotates in an opposite(counterclockwise) direction, springs 38 between the clutch rollers 34and inner race 36 are compressed, relieving the jam (i.e., releasing thelocking action) to permit the clutch rollers 34 to slip. As the clutchrollers 34 slip, the main wheel 24 rotates freely about the inner race36 such that no counterclockwise angular displacement of the main wheel24 is transmitted to the lead screw 32. Thus, in this embodiment, theclutch 28 transmits angular displacement of the main wheel 24 to thelead screw 32 only if the main wheel 24 and inner race 36 move in theclockwise direction when the clutch rollers 34 are wedged (jammed)between the surface of their respective tilted slope pockets 37 of themain wheel 24 and outer surface of the inner race 36.

With reference to FIG. 5, an exploded view of an embodiment of aminiature drug delivery pump, generally indicated by symbol 50 is shown,for example, with the SMA based pump drive 40 shown by FIG. 4. In allembodiments, the unidirectional rotational motion of the lead screw 32also causes rotation about the nut portion 43 of the plunger 42 causinglinear movement (translation) of the plunger 42 along the axis ofrotation X in a dispensing direction. Translation of the plunger 42 inthe dispensing direction advances the plunger piston 44 to dispense aliquid drug from the drug container 46.

As shown, the drug container 46 is accommodated in a cradle 48 of a base51 of the drug delivery pump 50. In one embodiment, the drug container46 is removable from the cradle 48 of the drug delivery pump 50, viaremoving a removable cap 52 from a cover 54 of the drug delivery pump 50which permits removing and replacing the drug container 46 via anopening 56 defined in the cover 54. In such an embodiment, the opening56 and/or the drug container 46 may be keyed or provided in shape whichensures proper alignment of the plunger piston 44 with the plunger 42.In another embodiment, the drug container 46 is not removable as thedrug delivery pump 50 in such an embodiment is intended to be disposableafter fully dispensing the liquid drug from the drug container 46.

In the illustrated embodiment of FIG. 5, the cover 54 snaps onto thebase 51 without requiring separate cover fasteners via projections 58 ofa pliable material which extend from the base 51 and resiliently seatinto notches 60 provided in the inside surface of the cover 54. In analternative embodiment separate cover fasteners may be provided.

The battery 62 is also provided to power the SMA based pump drive 40 ofthe drug delivery pump 50. The battery 62 in the illustrated embodimentis a size AAAA, which is about 42.5 mm long and about 8.3 mm indiameter, weighing around 6.5 grams. Output of alkaline batteries inthis size is 1.5 volts, 625 mA·h. Although elements in the figures maybe exaggerated in portion to other components, it is to be appreciatedthat the approximate relative size between the drug delivery pump 50 andthe battery 62 is intended to be shown in the embodiment illustrated byFIG. 5. Accordingly, as shown the drug delivery pump 50 is not muchlarger than the AAAA battery 62, and is in one embodiment about 61 mmlong, about 32 mm wide, and 15.5 mm in height, and weighs about oneounce, with the drug container 46 holding 2 ml of a liquid drug. Suchdimensions of the drug delivery pump 50 is about one fourth the size ofexisting conventional pumps. The small size and weight of the drugdelivery pump 50 makes it easier for the patient to hold the deliverypump in place, such via an adhesive on the skin and/or to conceal thedelivery pump under clothing.

The battery 62 is held in a battery cradle 64 provided in the base 51and contacts electrical terminal posts 66. The conductors 14 of the SMAbased pump drive 40 each connect between a respective one of theelectrical terminal posts 66 and the controller 25. A hole 70 isprovided in the cover 54 such that the push button 72 may be depressedto energize the SMA wire 12 of the SMA based pump drive 40. It is to beappreciated that other electrical/IC components are provided, but arenot shown for convenience of illustration as the actual control andelectrical system of the drug pump is not the focus of the presentinvention.

The lead screw 32 which extends through and supports the main wheel 24and the unidirectional clutch 28 about the axis of rotation X, issupported in turn by a base support 76 and the cradle 48. In addition,one or more of the projections 58 may serve to support the SMA basedpump drive 40 against rearward thrust, which may further be support inother directions (e.g., up, side-to-side) by other supports, such as astrapping 77. In this manner, motion by the SMA base pump drive 40,which is counter to the thrust and torque provided by the lead screw 32when rotated along the axis of rotation X, is minimized.

With reference to FIG. 6, an exploded view of particular components of aSMA based pump drive and their arrangement thereof according to anembodiment of the present invention is shown. The lead screw 32 in oneembodiment has a key portion 78 which fits into a slot 80 provided inthe inner race 36, such that the lead screw 32 rotates only with theinner race 36. The lead screw 32 is accommodated in a threaded cavity 82of the nut portion 43 of the plunger 42. As the SMA wire 12 of the pumpdrive is energized by depressing the push button 72 (FIG. 7), the leadscrew 32 rotates and advances out of the threaded cavity 82 along therotational axis X causing movement of the plunger 42. As mentioned abovepreviously, movement of the plunger 42 (i.e., translational along therotational axis X) advances the plunger piston 44 into the drugcontainer 46 (FIG. 5) to dispense a liquid drug therefrom. It is to beappreciated that in an alternative embodiment, the arrangement of thelead screw 32 and the plunger 42 used to push the plunger piston 44 isreversed. In such an alternative embodiment, the lead screw 32 providesthe threaded cavity 82 in which a threaded outer diameter (not shown) ofthe plunger 42 is accommodated. In still another embodiment, the innerrace 36 of the clutch 28 provides the threaded cavity 82 which actsdirectly on the threaded outer diameter of the plunger 42.

As shown by FIG. 7, in one embodiment, the drug delivery pump 50provides a scaled window 92 through which a portion of the plungerpiston 44 is visible and by which the patient in one embodiment uses tometer the delivery of a relatively large dose of the liquid drug. Inanother embodiment, dispensing of very small amounts of the liquid drugcan be provided by controlling the pump drive with a timed switchingcircuit of the controller 25, wherein depressing push button 72activates the timed switching circuit which energizes the pump drive fora predetermined period per button push. The drug container 46 includesan injection site 94 which is used to connect a spike connector 96 of anadministration set 98 to the drug delivery pump 50. The spike connector96 is connected to a fluid conduit 100 which at the distal end connectsto a catheter 102, which enters the patient's intravenous system throughthe skin for delivery of the liquid drug.

Although not limited to, some of the noted advantages of the presentinvention are as follows: the inherent precision of the motion from theSMA wire which can be used to accurately deliver very small doses (i.e.,about 0.01 ml), the ability to run at high frequency (up to 1 hz) todeliver quickly a large dose (i.e., about 1.0 ml), nearly silentoperation, fewer moving parts, and inexpensive parts. Such advantagesresult in an overall compact and low cost drug delivery pump for theconsumer.

The foregoing description of the invention has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise form disclosed, andother modifications and variations may be possible in light of the aboveteachings. The above embodiments disclosed were chosen and described toexplain the principles of the invention and its practical application tothereby enable others skilled in the art to best utilize the invention.It is intended that the appended claims be construed to include otheralternative embodiments of the invention except insofar as limited bythe prior art.

What is claimed is:
 1. A method of dispensing a liquid drug from acontainer having a plunger piston, said method comprises: providing alead screw having a rotational axis and operably connecting the leadscrew to the plunger piston wherein rotation of the lead screw about therotational axis advances the piston plunger in a dispensing directionwhich dispenses the liquid drug from the container; providing a wheel;providing a unidirectional clutch to support the wheel about therotational axis; connecting an inner race of the unidirectional clutchcentrally to the lead screw, wherein the unidirectional clutch isconfigured to rotate both the inner race and lead screw about therotational axis in unison with rotation of the wheel only in a firstrotational direction, and to let the wheel rotation relative to theinner race without rotating the lead screw about the rotational axis ina second rotational direction opposite to the first rotationaldirection; providing a first shape memory alloy wire providing a motorforce when excited to rotate the wheel in at least the first rotationaldirection; providing a second shape memory alloy wire providing a motorforce when excited to rotate the wheel in at least the second rotationaldirection; and exciting the shape memory alloy wires, wherein the firstshape memory alloy wire is mounted directly to a first spoke of thewheel, and the second shape memory alloy wire is mounted directly to asecond spoke of the wheel, wherein the first and second spokes extendparallel to the axis of rotation.
 2. A pump drive used to dispense aliquid drug from a container having a plunger piston, said pump drivecomprising: a lead screw having a rotational axis and being operablyconnected to the plunger piston, wherein rotation of the lead screwabout the rotational axis advances the piston plunger in a dispensingdirection which dispenses the liquid drug from the container; a wheel; aunidirectional clutch provided about the rotational axis and supportingcentrally the wheel, the unidirectional clutch having an inner raceconnected centrally to the lead screw, wherein the unidirectional clutchis configured to rotate both the inner race and lead screw about therotational axis in unison with rotation of the wheel in only a firstrotational direction, and to let the wheel rotate relative to the innerrace without rotating the lead screw about the rotational axis in asecond rotational direction opposite to the first rotational direction;a first shape memory alloy wire providing a motor force when excited torotate the wheel in at least the first rotational direction; and asecond shape memory alloy wire providing a motor force when excited torotate the wheel in at least the second rotational direction; whereinthe first shape memory wire is mounted directly to a first spoke of thewheel, and the second shape memory wire is mounted directly to a secondspoke of the wheel, wherein the first and second spokes extend parallelto the axis of rotation.
 3. The pump drive according to claim 2, whereinthe first shape memory alloy wire is a plurality of wires providing themotor force when excited to rotate the wheel in the first rotationaldirection, and the second shape memory alloy wire is a plurality ofwires providing the motor force when excited to rotate the wheel in thesecond rotational direction, each of said plurality of first and secondshape memory alloy wires is mounted directly to a spoke of the wheelwhich extends parallel to the axis of rotation.
 4. The pump driveaccording to claim 2, wherein the first shape memory alloy wire iswrapped around at least half the circumference of the wheel.
 5. The pumpdrive according to claim 2, wherein the second shape memory alloy wireis wrapped around at least half the circumference of the wheel.